Indication of fluid or liquid level is a critical variable in process control, storage tank monitoring, and mechanical systems where liquids are contained. Level monitoring systems for liquids typically comprise a transducer to convert liquid level to an appropriate level indicating variable or signal, a transmission medium for conveying the variable or signal, a receiver to accept and process the variable or signal, and a display for visual indication. Liquid level indication is of particular importance in the marine industry. For example, when boats travel in the open sea, an accurate indication of fuel quantity is an essential component to successful navigation. Thus, confidence in fuel indication accuracy is critical. Yet it is often the case that boat manufactures will use the same traditional form of level sensing across their entire line of boats, regardless of the application the boat is to used for, or its cost. Thus, boats costing hundreds of thousands of dollars use the same level sensing technology as less expensive boats.
A common problem with traditional level sensing technology is premature failure of the sending unit. The sending unit is the apparatus which provides a measure of liquid level within a tank. In the marine industry, the sensing components are frequently cemented into a liquid-tight stem using an epoxy or potting compound. This practice is problematic, however, because vibration and movement of the boat are conveyed to the sending unit. Thus, over time, the sending unit fails and requires replacement. Such premature failures are particularly problematic when a boat is far from port.
To compound the problem of failing sending units, space on boats is often at a premium. Thus, fuel tanks are frequently located in cramped engine. Thus, when a sending unit fails, it is difficult to access. Further, because traditional sending units are rigid (in order to protect the sensitive sensors along their length), extraction requires either removal of the fuel storage tank or cutting a hole in the floor of the deck to access the sending unit from above and to remove the unit on a straight vertical. Further, because traditional sending units are not designed to be bent, they inherently lack flexibility and their installed components crack and fail whenever the unit is subjected to a bending force.
Accordingly, what is needed is a sending unit that is robust, so as to withstand the harsh applications of marine use, is simple to replace and repair, and can withstand bending at acute angles and still function.